diff --git a/__tests__/__fixtures__/typecheck.ts b/__tests__/__fixtures__/typecheck.ts
index aaa1263..1664ba5 100644
--- a/__tests__/__fixtures__/typecheck.ts
+++ b/__tests__/__fixtures__/typecheck.ts
@@ -32,6 +32,17 @@ const cssWithFallbackValues: CSS.PropertiesFallback = {
   clip: [undefined],
 };
 
+const cssWithFallbackConstValues: CSS.PropertiesFallback = {
+  flexGrow: [1] as const,
+  flexShrink: [1] as const,
+  flexBasis: ['max-content'] as const,
+  flexDirection: ['row'] as const,
+  MozAppearance: ['button'] as const,
+  msOverflowStyle: ['scrollbar'] as const,
+  height: undefined,
+  clip: [undefined] as const,
+};
+
 const cssWithHyphenProperties: CSS.PropertiesHyphen = {
   'flex-grow': 1,
   'flex-shrink': 0,
@@ -149,6 +160,7 @@ const differentMajorVersions: CSS.Properties = {} as OldCSS.Properties;
 
 css;
 cssWithFallbackValues;
+cssWithFallbackConstValues;
 cssWithHyphenProperties;
 cssWithDifferentLength;
 unknownProperty;
diff --git a/__tests__/__snapshots__/dist.typescript-3.5.ts.snap b/__tests__/__snapshots__/dist.typescript-3.5.ts.snap
index 18c20f5..2016402 100644
--- a/__tests__/__snapshots__/dist.typescript-3.5.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-3.5.ts.snap
@@ -1,58 +1,64 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`Typescript 3.5 detects errors 1`] = `
-"31:2 - Type 'undefined[]' is not assignable to type '"auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | HyphenateCharacter[] | undefined'.
-  Type 'undefined[]' is not assignable to type 'HyphenateCharacter[]'.
+"31:2 - Type 'undefined[]' is not assignable to type '"auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | readonly HyphenateCharacter[] | undefined'.
+  Type 'undefined[]' is not assignable to type 'readonly HyphenateCharacter[]'.
     Type 'undefined' is not assignable to type 'HyphenateCharacter'."
 `;
 
 exports[`Typescript 3.5 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
-  Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
+"42:2 - Type 'readonly [undefined]' is not assignable to type '"auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | readonly HyphenateCharacter[] | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly HyphenateCharacter[]'.
+    Type 'undefined' is not assignable to type 'HyphenateCharacter'."
 `;
 
 exports[`Typescript 3.5 detects errors 3`] = `
-"52:2 - Type 'number[]' is not assignable to type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | undefined'.
-  Type 'number[]' is not assignable to type '"unset"'."
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+  Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
 exports[`Typescript 3.5 detects errors 4`] = `
-"53:2 - Type 'number[]' is not assignable to type '"inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | (number & {}) | undefined'.
+"63:2 - Type 'number[]' is not assignable to type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | undefined'.
   Type 'number[]' is not assignable to type '"unset"'."
 `;
 
 exports[`Typescript 3.5 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
-  Type '{}' is not assignable to type 'string'."
+"64:2 - Type 'number[]' is not assignable to type '"inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | (number & {}) | undefined'.
+  Type 'number[]' is not assignable to type '"unset"'."
 `;
 
 exports[`Typescript 3.5 detects errors 6`] = `
-"63:10 - Type 'Range' is not assignable to type '"auto"'.
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
+  Type '{}' is not assignable to type 'string'."
+`;
+
+exports[`Typescript 3.5 detects errors 7`] = `
+"74:10 - Type 'Range' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 3.5 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 3.5 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 3.5 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 3.5 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 3.5 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 3.5 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 3.5 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 3.5 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 3.5 detects errors 11`] = `
-"107:14 - Argument of type '1[]' is not assignable to parameter of type 'string | 0 | (string | 0)[]'.
+exports[`Typescript 3.5 detects errors 12`] = `
+"118:14 - Argument of type '1[]' is not assignable to parameter of type 'string | 0 | (string | 0)[]'.
   Type '1[]' is not assignable to type '(string | 0)[]'.
     Type '1' is not assignable to type 'string | 0'."
 `;
 
-exports[`Typescript 3.5 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 3.5 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 3.5 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 3.5 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 3.5 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
+exports[`Typescript 3.5 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
 
-exports[`Typescript 3.5 detects errors 15`] = `
-"145:34 - Argument of type '[1]' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'.
+exports[`Typescript 3.5 detects errors 16`] = `
+"156:34 - Argument of type '[1]' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'.
   Type '[1]' is not assignable to type '[0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 5 more ... | "min-intrinsic"]'.
     Type '1' is not assignable to type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 5 more ... | "min-intrinsic"'."
 `;
diff --git a/__tests__/__snapshots__/dist.typescript-3.6.ts.snap b/__tests__/__snapshots__/dist.typescript-3.6.ts.snap
index d704740..79b0d62 100644
--- a/__tests__/__snapshots__/dist.typescript-3.6.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-3.6.ts.snap
@@ -1,58 +1,64 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`Typescript 3.6 detects errors 1`] = `
-"31:2 - Type 'undefined[]' is not assignable to type '"auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | HyphenateCharacter[] | undefined'.
-  Type 'undefined[]' is not assignable to type 'HyphenateCharacter[]'.
+"31:2 - Type 'undefined[]' is not assignable to type '"auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | readonly HyphenateCharacter[] | undefined'.
+  Type 'undefined[]' is not assignable to type 'readonly HyphenateCharacter[]'.
     Type 'undefined' is not assignable to type 'HyphenateCharacter'."
 `;
 
 exports[`Typescript 3.6 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
-  Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
+"42:2 - Type 'readonly [undefined]' is not assignable to type '"auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | readonly HyphenateCharacter[] | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly HyphenateCharacter[]'.
+    Type 'undefined' is not assignable to type 'HyphenateCharacter'."
 `;
 
 exports[`Typescript 3.6 detects errors 3`] = `
-"52:2 - Type 'number[]' is not assignable to type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | undefined'.
-  Type 'number[]' is not assignable to type '"unset"'."
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+  Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
 exports[`Typescript 3.6 detects errors 4`] = `
-"53:2 - Type 'number[]' is not assignable to type '"inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | (number & {}) | undefined'.
+"63:2 - Type 'number[]' is not assignable to type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | undefined'.
   Type 'number[]' is not assignable to type '"unset"'."
 `;
 
 exports[`Typescript 3.6 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
-  Type '{}' is not assignable to type 'string'."
+"64:2 - Type 'number[]' is not assignable to type '"inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | (number & {}) | undefined'.
+  Type 'number[]' is not assignable to type '"unset"'."
 `;
 
 exports[`Typescript 3.6 detects errors 6`] = `
-"63:10 - Type 'Range' is not assignable to type '"auto"'.
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
+  Type '{}' is not assignable to type 'string'."
+`;
+
+exports[`Typescript 3.6 detects errors 7`] = `
+"74:10 - Type 'Range' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 3.6 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 3.6 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 3.6 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 3.6 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 3.6 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 3.6 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 3.6 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 3.6 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 3.6 detects errors 11`] = `
-"107:14 - Argument of type '1[]' is not assignable to parameter of type 'string | 0 | (string | 0)[]'.
+exports[`Typescript 3.6 detects errors 12`] = `
+"118:14 - Argument of type '1[]' is not assignable to parameter of type 'string | 0 | (string | 0)[]'.
   Type '1[]' is not assignable to type '(string | 0)[]'.
     Type '1' is not assignable to type 'string | 0'."
 `;
 
-exports[`Typescript 3.6 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 3.6 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 3.6 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 3.6 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 3.6 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
+exports[`Typescript 3.6 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
 
-exports[`Typescript 3.6 detects errors 15`] = `
-"145:34 - Argument of type '[1]' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'.
+exports[`Typescript 3.6 detects errors 16`] = `
+"156:34 - Argument of type '[1]' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'.
   Type '[1]' is not assignable to type '[0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 5 more ... | "min-intrinsic"]'.
     Type '1' is not assignable to type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 5 more ... | "min-intrinsic"'."
 `;
diff --git a/__tests__/__snapshots__/dist.typescript-3.7.ts.snap b/__tests__/__snapshots__/dist.typescript-3.7.ts.snap
index 337298a..cedb253 100644
--- a/__tests__/__snapshots__/dist.typescript-3.7.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-3.7.ts.snap
@@ -1,58 +1,64 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`Typescript 3.7 detects errors 1`] = `
-"31:2 - Type 'undefined[]' is not assignable to type '"auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | HyphenateCharacter[] | undefined'.
-  Type 'undefined[]' is not assignable to type 'HyphenateCharacter[]'.
+"31:2 - Type 'undefined[]' is not assignable to type '"auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | readonly HyphenateCharacter[] | undefined'.
+  Type 'undefined[]' is not assignable to type 'readonly HyphenateCharacter[]'.
     Type 'undefined' is not assignable to type 'HyphenateCharacter'."
 `;
 
 exports[`Typescript 3.7 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
-  Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
+"42:2 - Type 'readonly [undefined]' is not assignable to type '"auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | readonly HyphenateCharacter[] | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly HyphenateCharacter[]'.
+    Type 'undefined' is not assignable to type 'HyphenateCharacter'."
 `;
 
 exports[`Typescript 3.7 detects errors 3`] = `
-"52:2 - Type 'number[]' is not assignable to type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | undefined'.
-  Type 'number[]' is not assignable to type '"unset"'."
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+  Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
 exports[`Typescript 3.7 detects errors 4`] = `
-"53:2 - Type 'number[]' is not assignable to type '"inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | (number & {}) | undefined'.
+"63:2 - Type 'number[]' is not assignable to type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | undefined'.
   Type 'number[]' is not assignable to type '"unset"'."
 `;
 
 exports[`Typescript 3.7 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
-  Type '{}' is not assignable to type 'string'."
+"64:2 - Type 'number[]' is not assignable to type '"inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | (number & {}) | undefined'.
+  Type 'number[]' is not assignable to type '"unset"'."
 `;
 
 exports[`Typescript 3.7 detects errors 6`] = `
-"63:10 - Type 'Range' is not assignable to type '"auto"'.
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
+  Type '{}' is not assignable to type 'string'."
+`;
+
+exports[`Typescript 3.7 detects errors 7`] = `
+"74:10 - Type 'Range' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 3.7 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 3.7 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 3.7 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 3.7 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 3.7 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 3.7 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 3.7 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 3.7 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 3.7 detects errors 11`] = `
-"107:14 - Argument of type '1[]' is not assignable to parameter of type 'string | 0 | (string | 0)[]'.
+exports[`Typescript 3.7 detects errors 12`] = `
+"118:14 - Argument of type '1[]' is not assignable to parameter of type 'string | 0 | (string | 0)[]'.
   Type '1[]' is not assignable to type '(string | 0)[]'.
     Type '1' is not assignable to type 'string | 0'."
 `;
 
-exports[`Typescript 3.7 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 3.7 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 3.7 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 3.7 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 3.7 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
+exports[`Typescript 3.7 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
 
-exports[`Typescript 3.7 detects errors 15`] = `
-"145:34 - Argument of type '[1]' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'.
+exports[`Typescript 3.7 detects errors 16`] = `
+"156:34 - Argument of type '[1]' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'.
   Type '[1]' is not assignable to type '[0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 5 more ... | "min-intrinsic"]'.
     Type '1' is not assignable to type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 5 more ... | "min-intrinsic"'."
 `;
diff --git a/__tests__/__snapshots__/dist.typescript-3.8.ts.snap b/__tests__/__snapshots__/dist.typescript-3.8.ts.snap
index f57844e..a1e841a 100644
--- a/__tests__/__snapshots__/dist.typescript-3.8.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-3.8.ts.snap
@@ -3,38 +3,44 @@
 exports[`Typescript 3.8 detects errors 1`] = `"31:9 - Type 'undefined' is not assignable to type 'HyphenateCharacter'."`;
 
 exports[`Typescript 3.8 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+"42:2 - Type 'readonly [undefined]' is not assignable to type '"auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | readonly HyphenateCharacter[] | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly HyphenateCharacter[]'.
+    Type 'undefined' is not assignable to type 'HyphenateCharacter'."
+`;
+
+exports[`Typescript 3.8 detects errors 3`] = `
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
   Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
-exports[`Typescript 3.8 detects errors 3`] = `"52:11 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 3.8 detects errors 4`] = `"63:11 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 3.8 detects errors 4`] = `"53:10 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 3.8 detects errors 5`] = `"64:10 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 3.8 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
+exports[`Typescript 3.8 detects errors 6`] = `
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
   Type '{}' is not assignable to type 'string'."
 `;
 
-exports[`Typescript 3.8 detects errors 6`] = `
-"63:10 - Type 'Range' is not assignable to type '"auto"'.
+exports[`Typescript 3.8 detects errors 7`] = `
+"74:10 - Type 'Range' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 3.8 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 3.8 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 3.8 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 3.8 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 3.8 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 3.8 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 3.8 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 3.8 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 3.8 detects errors 11`] = `"107:15 - Type 'number' is not assignable to type 'string | 0'."`;
+exports[`Typescript 3.8 detects errors 12`] = `"118:15 - Type 'number' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 3.8 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 3.8 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 3.8 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 3.8 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 3.8 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
+exports[`Typescript 3.8 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
 
-exports[`Typescript 3.8 detects errors 15`] = `"145:35 - Type '1' is not assignable to type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 5 more ... | "min-intrinsic"'."`;
+exports[`Typescript 3.8 detects errors 16`] = `"156:35 - Type '1' is not assignable to type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 5 more ... | "min-intrinsic"'."`;
diff --git a/__tests__/__snapshots__/dist.typescript-3.9.ts.snap b/__tests__/__snapshots__/dist.typescript-3.9.ts.snap
index fbfa470..f39bdd0 100644
--- a/__tests__/__snapshots__/dist.typescript-3.9.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-3.9.ts.snap
@@ -3,38 +3,44 @@
 exports[`Typescript 3.9 detects errors 1`] = `"31:9 - Type 'undefined' is not assignable to type 'HyphenateCharacter'."`;
 
 exports[`Typescript 3.9 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+"42:2 - Type 'readonly [undefined]' is not assignable to type '"auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | readonly HyphenateCharacter[] | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly HyphenateCharacter[]'.
+    Type 'undefined' is not assignable to type 'HyphenateCharacter'."
+`;
+
+exports[`Typescript 3.9 detects errors 3`] = `
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
   Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
-exports[`Typescript 3.9 detects errors 3`] = `"52:11 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 3.9 detects errors 4`] = `"63:11 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 3.9 detects errors 4`] = `"53:10 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 3.9 detects errors 5`] = `"64:10 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 3.9 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
+exports[`Typescript 3.9 detects errors 6`] = `
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
   Type '{}' is not assignable to type 'string'."
 `;
 
-exports[`Typescript 3.9 detects errors 6`] = `
-"63:10 - Type 'Range' is not assignable to type '"auto"'.
+exports[`Typescript 3.9 detects errors 7`] = `
+"74:10 - Type 'Range' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 3.9 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 3.9 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 3.9 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 3.9 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 3.9 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 3.9 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 3.9 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 3.9 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 3.9 detects errors 11`] = `"107:15 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 3.9 detects errors 12`] = `"118:15 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 3.9 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 3.9 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 3.9 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 3.9 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 3.9 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
+exports[`Typescript 3.9 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
 
-exports[`Typescript 3.9 detects errors 15`] = `"145:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
+exports[`Typescript 3.9 detects errors 16`] = `"156:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
diff --git a/__tests__/__snapshots__/dist.typescript-4.0.ts.snap b/__tests__/__snapshots__/dist.typescript-4.0.ts.snap
index e54b418..b4507e0 100644
--- a/__tests__/__snapshots__/dist.typescript-4.0.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-4.0.ts.snap
@@ -3,38 +3,44 @@
 exports[`Typescript 4.0 detects errors 1`] = `"31:9 - Type 'undefined' is not assignable to type 'HyphenateCharacter'."`;
 
 exports[`Typescript 4.0 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+"42:2 - Type 'readonly [undefined]' is not assignable to type '"auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | readonly HyphenateCharacter[] | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly HyphenateCharacter[]'.
+    Type 'undefined' is not assignable to type 'HyphenateCharacter'."
+`;
+
+exports[`Typescript 4.0 detects errors 3`] = `
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
   Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
-exports[`Typescript 4.0 detects errors 3`] = `"52:11 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.0 detects errors 4`] = `"63:11 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.0 detects errors 4`] = `"53:10 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.0 detects errors 5`] = `"64:10 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.0 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
+exports[`Typescript 4.0 detects errors 6`] = `
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
   Type '{}' is not assignable to type 'string'."
 `;
 
-exports[`Typescript 4.0 detects errors 6`] = `
-"63:10 - Type 'Range' is not assignable to type '"auto"'.
+exports[`Typescript 4.0 detects errors 7`] = `
+"74:10 - Type 'Range' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 4.0 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.0 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.0 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.0 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.0 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.0 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.0 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 4.0 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 4.0 detects errors 11`] = `"107:15 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.0 detects errors 12`] = `"118:15 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.0 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.0 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.0 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.0 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.0 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
+exports[`Typescript 4.0 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
 
-exports[`Typescript 4.0 detects errors 15`] = `"145:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
+exports[`Typescript 4.0 detects errors 16`] = `"156:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
diff --git a/__tests__/__snapshots__/dist.typescript-4.1.ts.snap b/__tests__/__snapshots__/dist.typescript-4.1.ts.snap
index 6b38292..65515a2 100644
--- a/__tests__/__snapshots__/dist.typescript-4.1.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-4.1.ts.snap
@@ -3,38 +3,44 @@
 exports[`Typescript 4.1 detects errors 1`] = `"31:9 - Type 'undefined' is not assignable to type 'HyphenateCharacter'."`;
 
 exports[`Typescript 4.1 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+"42:2 - Type 'readonly [undefined]' is not assignable to type '"auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | readonly HyphenateCharacter[] | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly HyphenateCharacter[]'.
+    Type 'undefined' is not assignable to type 'HyphenateCharacter'."
+`;
+
+exports[`Typescript 4.1 detects errors 3`] = `
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
   Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
-exports[`Typescript 4.1 detects errors 3`] = `"52:11 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.1 detects errors 4`] = `"63:11 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.1 detects errors 4`] = `"53:10 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.1 detects errors 5`] = `"64:10 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.1 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
+exports[`Typescript 4.1 detects errors 6`] = `
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
   Type '{}' is not assignable to type 'string'."
 `;
 
-exports[`Typescript 4.1 detects errors 6`] = `
-"63:10 - Type 'Range' is not assignable to type '"auto"'.
+exports[`Typescript 4.1 detects errors 7`] = `
+"74:10 - Type 'Range' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 4.1 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.1 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.1 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.1 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.1 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.1 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.1 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 4.1 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 4.1 detects errors 11`] = `"107:15 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.1 detects errors 12`] = `"118:15 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.1 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.1 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.1 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.1 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.1 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
+exports[`Typescript 4.1 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type '0 | "auto" | "inherit" | (string & {}) | "-moz-initial" | "initial" | "revert" | "revert-layer" | "unset" | "-moz-fit-content" | "-moz-max-content" | "-moz-min-content" | "fit-content" | ... 6 more ... | [...]'."`;
 
-exports[`Typescript 4.1 detects errors 15`] = `"145:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
+exports[`Typescript 4.1 detects errors 16`] = `"156:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
diff --git a/__tests__/__snapshots__/dist.typescript-4.2.ts.snap b/__tests__/__snapshots__/dist.typescript-4.2.ts.snap
index f82bd18..d158ddc 100644
--- a/__tests__/__snapshots__/dist.typescript-4.2.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-4.2.ts.snap
@@ -3,38 +3,44 @@
 exports[`Typescript 4.2 detects errors 1`] = `"31:9 - Type 'undefined' is not assignable to type 'Clip'."`;
 
 exports[`Typescript 4.2 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+"42:2 - Type 'readonly [undefined]' is not assignable to type 'Clip | readonly Clip[] | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly Clip[]'.
+    Type 'undefined' is not assignable to type 'Clip'."
+`;
+
+exports[`Typescript 4.2 detects errors 3`] = `
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
   Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
-exports[`Typescript 4.2 detects errors 3`] = `"52:11 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.2 detects errors 4`] = `"63:11 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.2 detects errors 4`] = `"53:10 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.2 detects errors 5`] = `"64:10 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.2 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
+exports[`Typescript 4.2 detects errors 6`] = `
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
   Type '{}' is not assignable to type 'string'."
 `;
 
-exports[`Typescript 4.2 detects errors 6`] = `
-"63:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
+exports[`Typescript 4.2 detects errors 7`] = `
+"74:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 4.2 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.2 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.2 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.2 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.2 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.2 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.2 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 4.2 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 4.2 detects errors 11`] = `"107:15 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.2 detects errors 12`] = `"118:15 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.2 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.2 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.2 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.2 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.2 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
+exports[`Typescript 4.2 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
 
-exports[`Typescript 4.2 detects errors 15`] = `"145:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
+exports[`Typescript 4.2 detects errors 16`] = `"156:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
diff --git a/__tests__/__snapshots__/dist.typescript-4.3.ts.snap b/__tests__/__snapshots__/dist.typescript-4.3.ts.snap
index f362d0f..8f964a0 100644
--- a/__tests__/__snapshots__/dist.typescript-4.3.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-4.3.ts.snap
@@ -3,38 +3,44 @@
 exports[`Typescript 4.3 detects errors 1`] = `"31:9 - Type 'undefined' is not assignable to type 'Clip'."`;
 
 exports[`Typescript 4.3 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+"42:2 - Type 'readonly [undefined]' is not assignable to type 'Clip | readonly Clip[] | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly Clip[]'.
+    Type 'undefined' is not assignable to type 'Clip'."
+`;
+
+exports[`Typescript 4.3 detects errors 3`] = `
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
   Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
-exports[`Typescript 4.3 detects errors 3`] = `"52:11 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.3 detects errors 4`] = `"63:11 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.3 detects errors 4`] = `"53:10 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.3 detects errors 5`] = `"64:10 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.3 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
+exports[`Typescript 4.3 detects errors 6`] = `
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
   Type '{}' is not assignable to type 'string'."
 `;
 
-exports[`Typescript 4.3 detects errors 6`] = `
-"63:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
+exports[`Typescript 4.3 detects errors 7`] = `
+"74:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 4.3 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.3 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.3 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.3 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.3 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.3 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.3 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 4.3 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 4.3 detects errors 11`] = `"107:15 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.3 detects errors 12`] = `"118:15 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.3 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.3 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.3 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.3 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.3 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
+exports[`Typescript 4.3 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
 
-exports[`Typescript 4.3 detects errors 15`] = `"145:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
+exports[`Typescript 4.3 detects errors 16`] = `"156:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
diff --git a/__tests__/__snapshots__/dist.typescript-4.4.ts.snap b/__tests__/__snapshots__/dist.typescript-4.4.ts.snap
index e1162d0..dbc94fe 100644
--- a/__tests__/__snapshots__/dist.typescript-4.4.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-4.4.ts.snap
@@ -3,38 +3,44 @@
 exports[`Typescript 4.4 detects errors 1`] = `"31:9 - Type 'undefined' is not assignable to type 'Clip'."`;
 
 exports[`Typescript 4.4 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+"42:2 - Type 'readonly [undefined]' is not assignable to type 'Clip | readonly Clip[] | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly Clip[]'.
+    Type 'undefined' is not assignable to type 'Clip'."
+`;
+
+exports[`Typescript 4.4 detects errors 3`] = `
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
   Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
-exports[`Typescript 4.4 detects errors 3`] = `"52:11 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.4 detects errors 4`] = `"63:11 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.4 detects errors 4`] = `"53:10 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.4 detects errors 5`] = `"64:10 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.4 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
+exports[`Typescript 4.4 detects errors 6`] = `
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
   Type '{}' is not assignable to type 'string'."
 `;
 
-exports[`Typescript 4.4 detects errors 6`] = `
-"63:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
+exports[`Typescript 4.4 detects errors 7`] = `
+"74:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 4.4 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.4 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.4 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.4 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.4 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.4 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.4 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 4.4 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 4.4 detects errors 11`] = `"107:15 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.4 detects errors 12`] = `"118:15 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.4 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.4 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.4 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.4 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.4 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
+exports[`Typescript 4.4 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
 
-exports[`Typescript 4.4 detects errors 15`] = `"145:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
+exports[`Typescript 4.4 detects errors 16`] = `"156:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
diff --git a/__tests__/__snapshots__/dist.typescript-4.5.ts.snap b/__tests__/__snapshots__/dist.typescript-4.5.ts.snap
index a715679..334ebca 100644
--- a/__tests__/__snapshots__/dist.typescript-4.5.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-4.5.ts.snap
@@ -3,38 +3,44 @@
 exports[`Typescript 4.5 detects errors 1`] = `"31:9 - Type 'undefined' is not assignable to type 'Clip'."`;
 
 exports[`Typescript 4.5 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+"42:2 - Type 'readonly [undefined]' is not assignable to type 'Clip | readonly Clip[] | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly Clip[]'.
+    Type 'undefined' is not assignable to type 'Clip'."
+`;
+
+exports[`Typescript 4.5 detects errors 3`] = `
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
   Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
-exports[`Typescript 4.5 detects errors 3`] = `"52:11 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.5 detects errors 4`] = `"63:11 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.5 detects errors 4`] = `"53:10 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.5 detects errors 5`] = `"64:10 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.5 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
+exports[`Typescript 4.5 detects errors 6`] = `
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
   Type '{}' is not assignable to type 'string'."
 `;
 
-exports[`Typescript 4.5 detects errors 6`] = `
-"63:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
+exports[`Typescript 4.5 detects errors 7`] = `
+"74:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 4.5 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.5 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.5 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.5 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.5 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.5 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.5 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 4.5 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 4.5 detects errors 11`] = `"107:15 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.5 detects errors 12`] = `"118:15 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.5 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.5 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.5 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.5 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.5 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
+exports[`Typescript 4.5 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
 
-exports[`Typescript 4.5 detects errors 15`] = `"145:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
+exports[`Typescript 4.5 detects errors 16`] = `"156:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
diff --git a/__tests__/__snapshots__/dist.typescript-4.6.ts.snap b/__tests__/__snapshots__/dist.typescript-4.6.ts.snap
index 6762be5..5607e69 100644
--- a/__tests__/__snapshots__/dist.typescript-4.6.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-4.6.ts.snap
@@ -3,38 +3,44 @@
 exports[`Typescript 4.6 detects errors 1`] = `"31:9 - Type 'undefined' is not assignable to type 'Clip'."`;
 
 exports[`Typescript 4.6 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+"42:2 - Type 'readonly [undefined]' is not assignable to type 'Clip | readonly Clip[] | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly Clip[]'.
+    Type 'undefined' is not assignable to type 'Clip'."
+`;
+
+exports[`Typescript 4.6 detects errors 3`] = `
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
   Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
-exports[`Typescript 4.6 detects errors 3`] = `"52:11 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.6 detects errors 4`] = `"63:11 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.6 detects errors 4`] = `"53:10 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.6 detects errors 5`] = `"64:10 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.6 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
+exports[`Typescript 4.6 detects errors 6`] = `
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
   Type '{}' is not assignable to type 'string'."
 `;
 
-exports[`Typescript 4.6 detects errors 6`] = `
-"63:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
+exports[`Typescript 4.6 detects errors 7`] = `
+"74:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 4.6 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.6 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.6 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.6 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.6 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.6 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.6 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 4.6 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 4.6 detects errors 11`] = `"107:15 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.6 detects errors 12`] = `"118:15 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.6 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.6 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.6 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.6 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.6 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
+exports[`Typescript 4.6 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
 
-exports[`Typescript 4.6 detects errors 15`] = `"145:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
+exports[`Typescript 4.6 detects errors 16`] = `"156:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
diff --git a/__tests__/__snapshots__/dist.typescript-4.7.ts.snap b/__tests__/__snapshots__/dist.typescript-4.7.ts.snap
index 0e4b9e3..71d6ffe 100644
--- a/__tests__/__snapshots__/dist.typescript-4.7.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-4.7.ts.snap
@@ -3,38 +3,44 @@
 exports[`Typescript 4.7 detects errors 1`] = `"31:9 - Type 'undefined' is not assignable to type 'Clip'."`;
 
 exports[`Typescript 4.7 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+"42:2 - Type 'readonly [undefined]' is not assignable to type 'Clip | readonly Clip[] | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly Clip[]'.
+    Type 'undefined' is not assignable to type 'Clip'."
+`;
+
+exports[`Typescript 4.7 detects errors 3`] = `
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
   Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
-exports[`Typescript 4.7 detects errors 3`] = `"52:11 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.7 detects errors 4`] = `"63:11 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.7 detects errors 4`] = `"53:10 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.7 detects errors 5`] = `"64:10 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.7 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
+exports[`Typescript 4.7 detects errors 6`] = `
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
   Type '{}' is not assignable to type 'string'."
 `;
 
-exports[`Typescript 4.7 detects errors 6`] = `
-"63:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
+exports[`Typescript 4.7 detects errors 7`] = `
+"74:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 4.7 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.7 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.7 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.7 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.7 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.7 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.7 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 4.7 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 4.7 detects errors 11`] = `"107:15 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.7 detects errors 12`] = `"118:15 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.7 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.7 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.7 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.7 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.7 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
+exports[`Typescript 4.7 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
 
-exports[`Typescript 4.7 detects errors 15`] = `"145:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
+exports[`Typescript 4.7 detects errors 16`] = `"156:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
diff --git a/__tests__/__snapshots__/dist.typescript-4.8.ts.snap b/__tests__/__snapshots__/dist.typescript-4.8.ts.snap
index 02afef9..2867092 100644
--- a/__tests__/__snapshots__/dist.typescript-4.8.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-4.8.ts.snap
@@ -3,38 +3,44 @@
 exports[`Typescript 4.8 detects errors 1`] = `"31:9 - Type 'undefined' is not assignable to type 'string'."`;
 
 exports[`Typescript 4.8 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+"42:2 - Type 'readonly [undefined]' is not assignable to type 'readonly string[] | Clip | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly string[]'.
+    Type 'undefined' is not assignable to type 'string'."
+`;
+
+exports[`Typescript 4.8 detects errors 3`] = `
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
   Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
-exports[`Typescript 4.8 detects errors 3`] = `"52:11 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.8 detects errors 4`] = `"63:11 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.8 detects errors 4`] = `"53:10 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.8 detects errors 5`] = `"64:10 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.8 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
+exports[`Typescript 4.8 detects errors 6`] = `
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
   Type '{}' is not assignable to type 'string'."
 `;
 
-exports[`Typescript 4.8 detects errors 6`] = `
-"63:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
+exports[`Typescript 4.8 detects errors 7`] = `
+"74:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 4.8 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.8 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.8 detects errors 8`] = `"82:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.8 detects errors 9`] = `"93:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.8 detects errors 9`] = `"96:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.8 detects errors 10`] = `"107:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.8 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 4.8 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 4.8 detects errors 11`] = `"107:15 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.8 detects errors 12`] = `"118:15 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.8 detects errors 12`] = `"120:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.8 detects errors 13`] = `"131:23 - This condition will always return 'false' since the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.8 detects errors 13`] = `"134:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.8 detects errors 14`] = `"145:25 - This condition will always return 'false' since the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.8 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
+exports[`Typescript 4.8 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
 
-exports[`Typescript 4.8 detects errors 15`] = `"145:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
+exports[`Typescript 4.8 detects errors 16`] = `"156:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
diff --git a/__tests__/__snapshots__/dist.typescript-4.9.ts.snap b/__tests__/__snapshots__/dist.typescript-4.9.ts.snap
index 39a6e5d..fff5036 100644
--- a/__tests__/__snapshots__/dist.typescript-4.9.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-4.9.ts.snap
@@ -3,38 +3,44 @@
 exports[`Typescript 4.9 detects errors 1`] = `"31:9 - Type 'undefined' is not assignable to type 'string'."`;
 
 exports[`Typescript 4.9 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+"42:2 - Type 'readonly [undefined]' is not assignable to type 'readonly string[] | Clip | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly string[]'.
+    Type 'undefined' is not assignable to type 'string'."
+`;
+
+exports[`Typescript 4.9 detects errors 3`] = `
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
   Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
-exports[`Typescript 4.9 detects errors 3`] = `"52:11 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.9 detects errors 4`] = `"63:11 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.9 detects errors 4`] = `"53:10 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 4.9 detects errors 5`] = `"64:10 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 4.9 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
+exports[`Typescript 4.9 detects errors 6`] = `
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
   Type '{}' is not assignable to type 'string'."
 `;
 
-exports[`Typescript 4.9 detects errors 6`] = `
-"63:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
+exports[`Typescript 4.9 detects errors 7`] = `
+"74:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 4.9 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.9 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.9 detects errors 8`] = `"82:23 - This comparison appears to be unintentional because the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.9 detects errors 9`] = `"93:23 - This comparison appears to be unintentional because the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.9 detects errors 9`] = `"96:25 - This comparison appears to be unintentional because the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.9 detects errors 10`] = `"107:25 - This comparison appears to be unintentional because the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.9 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 4.9 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 4.9 detects errors 11`] = `"107:15 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 4.9 detects errors 12`] = `"118:15 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 4.9 detects errors 12`] = `"120:23 - This comparison appears to be unintentional because the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 4.9 detects errors 13`] = `"131:23 - This comparison appears to be unintentional because the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 4.9 detects errors 13`] = `"134:25 - This comparison appears to be unintentional because the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 4.9 detects errors 14`] = `"145:25 - This comparison appears to be unintentional because the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 4.9 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
+exports[`Typescript 4.9 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
 
-exports[`Typescript 4.9 detects errors 15`] = `"145:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
+exports[`Typescript 4.9 detects errors 16`] = `"156:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
diff --git a/__tests__/__snapshots__/dist.typescript-latest.ts.snap b/__tests__/__snapshots__/dist.typescript-latest.ts.snap
index 2993c10..b485663 100644
--- a/__tests__/__snapshots__/dist.typescript-latest.ts.snap
+++ b/__tests__/__snapshots__/dist.typescript-latest.ts.snap
@@ -3,38 +3,44 @@
 exports[`Typescript 5.0 detects errors 1`] = `"31:9 - Type 'undefined' is not assignable to type 'string'."`;
 
 exports[`Typescript 5.0 detects errors 2`] = `
-"48:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
+"42:2 - Type 'readonly [undefined]' is not assignable to type 'readonly string[] | Clip | undefined'.
+  Type 'readonly [undefined]' is not assignable to type 'readonly string[]'.
+    Type 'undefined' is not assignable to type 'string'."
+`;
+
+exports[`Typescript 5.0 detects errors 3`] = `
+"59:2 - Type '{ unknownProperty: number; }' is not assignable to type 'Properties<0 | (string & {}), string & {}>'.
   Object literal may only specify known properties, and 'unknownProperty' does not exist in type 'Properties<0 | (string & {}), string & {}>'."
 `;
 
-exports[`Typescript 5.0 detects errors 3`] = `"52:11 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 5.0 detects errors 4`] = `"63:11 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 5.0 detects errors 4`] = `"53:10 - Type 'number' is not assignable to type 'string'."`;
+exports[`Typescript 5.0 detects errors 5`] = `"64:10 - Type 'number' is not assignable to type 'string'."`;
 
-exports[`Typescript 5.0 detects errors 5`] = `
-"58:6 - Type '{}' is not assignable to type 'string & {}'.
+exports[`Typescript 5.0 detects errors 6`] = `
+"69:6 - Type '{}' is not assignable to type 'string & {}'.
   Type '{}' is not assignable to type 'string'."
 `;
 
-exports[`Typescript 5.0 detects errors 6`] = `
-"63:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
+exports[`Typescript 5.0 detects errors 7`] = `
+"74:10 - Type '"auto" | (string & {})' is not assignable to type '"auto"'.
   Type 'string & {}' is not assignable to type '"auto"'."
 `;
 
-exports[`Typescript 5.0 detects errors 7`] = `"70:6 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 5.0 detects errors 8`] = `"81:6 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 5.0 detects errors 8`] = `"82:23 - This comparison appears to be unintentional because the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 5.0 detects errors 9`] = `"93:23 - This comparison appears to be unintentional because the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 5.0 detects errors 9`] = `"96:25 - This comparison appears to be unintentional because the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 5.0 detects errors 10`] = `"107:25 - This comparison appears to be unintentional because the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 5.0 detects errors 10`] = `"106:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
+exports[`Typescript 5.0 detects errors 11`] = `"117:14 - Argument of type '1' is not assignable to parameter of type 'string | 0 | (string | 0)[]'."`;
 
-exports[`Typescript 5.0 detects errors 11`] = `"107:15 - Type '1' is not assignable to type 'string | 0'."`;
+exports[`Typescript 5.0 detects errors 12`] = `"118:15 - Type '1' is not assignable to type 'string | 0'."`;
 
-exports[`Typescript 5.0 detects errors 12`] = `"120:23 - This comparison appears to be unintentional because the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
+exports[`Typescript 5.0 detects errors 13`] = `"131:23 - This comparison appears to be unintentional because the types 'string | 0 | (string | 0)[]' and '1' have no overlap."`;
 
-exports[`Typescript 5.0 detects errors 13`] = `"134:25 - This comparison appears to be unintentional because the types 'string | 0' and '1' have no overlap."`;
+exports[`Typescript 5.0 detects errors 14`] = `"145:25 - This comparison appears to be unintentional because the types 'string | 0' and '1' have no overlap."`;
 
-exports[`Typescript 5.0 detects errors 14`] = `"144:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
+exports[`Typescript 5.0 detects errors 15`] = `"155:34 - Argument of type '1' is not assignable to parameter of type 'Width<0 | (string & {})> | [Width<0 | (string & {})>]'."`;
 
-exports[`Typescript 5.0 detects errors 15`] = `"145:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
+exports[`Typescript 5.0 detects errors 16`] = `"156:35 - Type '1' is not assignable to type 'Width<0 | (string & {})>'."`;
diff --git a/__tests__/dist.typescript-3.5.ts b/__tests__/dist.typescript-3.5.ts
index d5e07a0..a3a6a0b 100644
--- a/__tests__/dist.typescript-3.5.ts
+++ b/__tests__/dist.typescript-3.5.ts
@@ -14,7 +14,7 @@ describe('Typescript 3.5', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(3.5);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-3.6.ts b/__tests__/dist.typescript-3.6.ts
index d19b516..dfb02fe 100644
--- a/__tests__/dist.typescript-3.6.ts
+++ b/__tests__/dist.typescript-3.6.ts
@@ -14,7 +14,7 @@ describe('Typescript 3.6', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(3.6);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-3.7.ts b/__tests__/dist.typescript-3.7.ts
index 58e9015..a49293d 100644
--- a/__tests__/dist.typescript-3.7.ts
+++ b/__tests__/dist.typescript-3.7.ts
@@ -14,7 +14,7 @@ describe('Typescript 3.7', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(3.7);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-3.8.ts b/__tests__/dist.typescript-3.8.ts
index 9ab85a6..3752258 100644
--- a/__tests__/dist.typescript-3.8.ts
+++ b/__tests__/dist.typescript-3.8.ts
@@ -14,7 +14,7 @@ describe('Typescript 3.8', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(3.8);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-3.9.ts b/__tests__/dist.typescript-3.9.ts
index b3f86e6..1615118 100644
--- a/__tests__/dist.typescript-3.9.ts
+++ b/__tests__/dist.typescript-3.9.ts
@@ -14,7 +14,7 @@ describe('Typescript 3.9', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(3.9);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-4.0.ts b/__tests__/dist.typescript-4.0.ts
index f8c6c65..6752f72 100644
--- a/__tests__/dist.typescript-4.0.ts
+++ b/__tests__/dist.typescript-4.0.ts
@@ -14,7 +14,7 @@ describe('Typescript 4.0', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(4.0);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-4.1.ts b/__tests__/dist.typescript-4.1.ts
index af578dd..0c48b3e 100644
--- a/__tests__/dist.typescript-4.1.ts
+++ b/__tests__/dist.typescript-4.1.ts
@@ -14,7 +14,7 @@ describe('Typescript 4.1', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(4.1);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-4.2.ts b/__tests__/dist.typescript-4.2.ts
index 94f3ab3..350bdda 100644
--- a/__tests__/dist.typescript-4.2.ts
+++ b/__tests__/dist.typescript-4.2.ts
@@ -14,7 +14,7 @@ describe('Typescript 4.2', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(4.2);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-4.3.ts b/__tests__/dist.typescript-4.3.ts
index c12be66..5373ba2 100644
--- a/__tests__/dist.typescript-4.3.ts
+++ b/__tests__/dist.typescript-4.3.ts
@@ -14,7 +14,7 @@ describe('Typescript 4.3', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(4.3);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-4.4.ts b/__tests__/dist.typescript-4.4.ts
index 2cee6bc..2b514e3 100644
--- a/__tests__/dist.typescript-4.4.ts
+++ b/__tests__/dist.typescript-4.4.ts
@@ -14,7 +14,7 @@ describe('Typescript 4.4', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(4.4);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-4.5.ts b/__tests__/dist.typescript-4.5.ts
index 426ac2f..0f3061f 100644
--- a/__tests__/dist.typescript-4.5.ts
+++ b/__tests__/dist.typescript-4.5.ts
@@ -14,7 +14,7 @@ describe('Typescript 4.5', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(4.5);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-4.6.ts b/__tests__/dist.typescript-4.6.ts
index 76029cc..9bbd2b9 100644
--- a/__tests__/dist.typescript-4.6.ts
+++ b/__tests__/dist.typescript-4.6.ts
@@ -14,7 +14,7 @@ describe('Typescript 4.6', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(4.6);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-4.7.ts b/__tests__/dist.typescript-4.7.ts
index ad2775a..a713b48 100644
--- a/__tests__/dist.typescript-4.7.ts
+++ b/__tests__/dist.typescript-4.7.ts
@@ -14,7 +14,7 @@ describe('Typescript 4.7', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(4.7);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-4.8.ts b/__tests__/dist.typescript-4.8.ts
index 4bf5b0e..5387ceb 100644
--- a/__tests__/dist.typescript-4.8.ts
+++ b/__tests__/dist.typescript-4.8.ts
@@ -14,7 +14,7 @@ describe('Typescript 4.8', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(4.8);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-4.9.ts b/__tests__/dist.typescript-4.9.ts
index 6ad8c03..8a38004 100644
--- a/__tests__/dist.typescript-4.9.ts
+++ b/__tests__/dist.typescript-4.9.ts
@@ -14,7 +14,7 @@ describe('Typescript 4.9', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(4.9);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/__tests__/dist.typescript-latest.ts b/__tests__/dist.typescript-latest.ts
index 3f17cb3..6447731 100644
--- a/__tests__/dist.typescript-latest.ts
+++ b/__tests__/dist.typescript-latest.ts
@@ -14,7 +14,7 @@ describe('Typescript 5.0', () => {
     });
 
     expect(Number(ts.versionMajorMinor)).toBe(5.0);
-    expect(errors.length).toBe(15);
+    expect(errors.length).toBe(16);
     for (const error of errors) {
       expect(error).toMatchSnapshot();
     }
diff --git a/index.d.ts b/index.d.ts
index 4f83c67..0f6ced6 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -6,7 +6,7 @@ export type PropertyValue<TValue> = TValue extends Array<infer AValue>
   ? TUnpacked
   : TValue;
 
-export type Fallback<T> = { [P in keyof T]: T[P] | NonNullable<T[P]>[] };
+export type Fallback<T> = { [P in keyof T]: T[P] | readonly NonNullable<T[P]>[] };
 
 export interface StandardLonghandProperties<TLength = (string & {}) | 0, TTime = string & {}> {
   /**
diff --git a/src/typescript.ts b/src/typescript.ts
index 5bd965b..ac369b2 100644
--- a/src/typescript.ts
+++ b/src/typescript.ts
@@ -70,7 +70,7 @@ export default async function typescript() {
     'TValue extends infer TUnpacked & {} ? TUnpacked : TValue' +
     ';' +
     EOL;
-  const fallback = 'export type Fallback<T> = { [P in keyof T]: T[P] | NonNullable<T[P]>[] };' + EOL;
+  const fallback = 'export type Fallback<T> = { [P in keyof T]: T[P] | readonly NonNullable<T[P]>[] };' + EOL;
 
   return (
     disableAutoExport +